2014/02/07

Corvettes and air defence

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The "corvette week" CIMSEC's "Next War" blog is a thing of the past, but the small surface combatant discussions are still among naval enthusiast's and professionals' favourite topics. OPVs and corvettes have this sexiness of small size and are untainted by the ludicrous costs of the capital ships (American DDGs, CVs of all kinds, SSNs).

The [corvette] flotillas operate in the littoral while the carrier and destroyers operate further back. They provide support such as AEW, helicopters, and long range missiles to prevent bombers and other aircraft from picking off the flotilla ships at their leisure.

This seems to address what was pointed out during CIMSEC's corvette week regarding the LGB threat.

A destroyers' (DDG) surface-to-air missile (SAM) defence might be a rather short leash, though. A flight of "bombers" with a couple of glide bombs with relatively cheap guidance packages could lob these glide bombs from low altitude and from beyond the corvette's own SAM envelope. A low altitude approach would defeat the semi-active radar guidance of SM-2 missiles at a much, much shorter distance than their notional range. This may be less than 10 nm*: A rather short leash.

The new and still extremely rare SM-6 missiles, the more numerous Aster missiles (active seeker requiring no radar illumination, just some target data) or small surface combatants with an organic radar illumination capability (typically coupled with ESSM, a rather ASW frigate-level SAM) would change the scenario a lot, but few SM-6 can be carried in addition to all the other purposeful missiles in a DDG's VLS.

SAMs and AAMs (both SM-6 and Aster have AAM-derived seekers) have track records of often disappointing hit percentages. They cannot always be used to good effect near the limits of their envelope when you need them because baiting tactics provoke their wasteful expenditure and the control centres accordingly need to be cautious with the expenditure of very expensive and scarce missiles.

The capital ships' security against the missile threat is debatable; their ability to project this security far to the benefit of small surface combatants is even more debatable.**

The fixation on anti-ship cruise missiles (sea skimmers and more Soviet-style supersonic missiles***) is probably ill-advised anyway. It was the a big thing after the Exocet missiles' successes in the Falklands War and plenty more or less expensive countermeasures were developed and deployed to counter them. Ever since the Millennium Challenge 2002 exercise (in which imaginary Iraqi speedboats overwhelmed and sank a fleet) speedboats are the big countermeasure provocateurs. This semi-ludicrous 'threat' is about to give way to guided ballistic missiles as favourite countermeasure provocateurs and thus military-industrial-complex money guarantors. Maybe hypervelocity (air-breathing) missiles will be the big money printing presses to Western navies and their contractors in the 2020's. There are plenty above-surface threats.

Naval discussions appear to still use the Exocet-like threat missile as a kind of default and favourite threat. Submarine fans and operators disagree and the history of anti-ship munitions development post-1945 indicates that Exocet-like threat missiles are but one threat of many, and apparently the one which provoked the most thorough countermeasures so far. We (or they) should pay more attention to the other threats.A defence against munitions alone instead of against platforms is going to fail if said munitions are cheap and defence is still difficult (and thus still not cheap).

*: The lobbing of a glide bomb at Mach 0.7 from very low altitude allows for ten or more nautical miles glide range (the kinetic energy is about the equivalent of 9,000 ft if I didn't mess up the calculation). This would be enough to stay far outside a typical corvette's air defence reach. Even ESSM-equipped ASW frigates may be at risk when challenged by such a tactic.The radar horizon for radar illumination is about 17 nm against very low level targets. 17 nm - 5 nm = 12 nm, subtract the glide range from this or at least the corvette's effective air defence range of usually no more than 4 nm. The result is less than 10 nm.**: And the USN may have horribly failed in its very belated introduction of active radar-guided SAMs. This was likely a consequence of the initially admirable performance of the AEGIS/SM-2 combo and similar to how the French army stuck for too long with its initially revolutionary, but soon surpassed 75 mm field cannons.***: Not attracting the most attention, but very interesting conceptually: 3M-54 Klub

13 comments:

Wouldn't the defense be to shoot down the plane doing the laser designation. I'm not sure what the designator's range is. In the relatively benign environment we usually see, if a plane is doing the designation, it is at medium altitude and not that far from the target, rather than at low altitude at the horizon. Any info on this extreme case?

It's not about SAL in the lob attack scenario, but about the range of fire&forget (and thus potentially non-line-of-sight) seekers.IIR, E/O, UV, mmW-radar, LIDAR/LADAR, passive radar&home-on-jam, cheap radar, INS - you could even lob a torpedo which begins to home in on the ship after entering the water.

As a freak scenario, it would also be possible to eject (during the lobbing attacks zenith) a laser target designator with some sensor suspended on a self-inflating balloon in a cloud of chaff - many defensive suites would need to be modified at least in their software before they would be effective against this within seconds (because they usually ignore such slowly floating objects to counter chaff).

There's so much more possible than Exocet and Brahmos-style missiles only. The Next War blog article used the LGB example for simplicity; it wasn't meant to be comprehensive.

I am not convinced about the LGB threat - the argument follows the pattern of many straw man arguments and ignores what the rest of the naval force is doing (and has done) to set up the engagements you envision.

In the scenario you describe, one must assume a competent naval commander who has conducted an effective strike warfare campaign which targets enemy C4-ISR networks, shore defenses, radars, and of course air fields with multiple cruise missile attacks. Then of course there are the efforts of the broader air campaign where air force and naval air craft have engaged the enemy as well.

It is hard to imagine that small warships would be sent into coastal waters absent some sort of combat air patrol aircraft, if there was a significant threat of enemy bombers being freed to conduct the type of strikes you describe. It also ignores the effect of EW, which will likely work against the enemy as active searches of even coastal waters will require significant use of radar. Fixed land installations are easy to target by the fleet, because they are fixed.

It is also difficult to imagine an enemy facing a substantial fleet off his shores deciding to target attrition units like corvettes, instead of trying to find and destroy major elements of the fleet. This is particularly the case when the fleet is striking targets in the enemy homeland.

Of course air superiority or sea control does not ensure the enemy is unable to mount any offensive action. I also discount the effectiveness of surface ships against submarines in a tactical engagement (your blog on targeting submarine shore facilities is excellent!).

I think that it is unfair to set up a scenario where the enemy is given every advantage and use that as the sole basis of a value judgment!

The effectiveness of small warships is not what they can achieve by themselves, but what their addition brings to the fleet.

If small warships are able to deal with threats like mines, PGMs, small boat swarms, submarines as well as routine patrol duties, then they add value by ridding major combatants from the tasks and risks associated such missions.

There is also the value of numbers, but only if the smaller combatants are able to contribute to the fight. There are systems like Cooperative Engagement that enable this.

Conversely, the engineering argument is that fewer, much larger ships are better able to support weapons and all important sensors – small combatants will never be able to support the same sensor capability as larger warships. The real fight is over access to targeting data.

Well, you described a scenario in which all the battlefield shaping had succeeded by textbook and corvettes didn't even need to fear a flight of strike fighters any more. That was a pointless scenario, as nobody would need corvettes if they were only survivable after victory was assured like that.

I'm interested in how to shape the battlefield for winning the campaign, and this means the corvettes still face the full hostile repertoire.

I understand that corvettes can contribute something (and wrote about it before http://cimsec.org/case-pickets/ ) but there is a fundamental problem with the fact that proper self-defence requires a minimum defensive suite that known corvettes typically don't possess.Meanwhile, any combined arms approach in which some platforms rely on others for aspects of their defence gravitates a lot towards much smaller boats than anyone would call "corvette".

I've been trying to point this fundamental issue out to the "smaller warships!" fashionistas, but even such basic issues as the full range of threats require elaboration in this debate.

"...there is a fundamental problem with the fact that proper self-defence requires a minimum defensive suite that known corvettes typically don't possess."

I strongly agree.

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“…you described a scenario in which all the battlefield shaping had succeeded by textbook…”

Naval forces have historically fought at a significant disadvantage against land-forces –why is the blue water force going to approach an enemy coastline unless it has the capability to subject the enemy defenses to overwhelming strikes by aircraft and cruise missiles?

No inferior naval force, including a carrier task force, is going to survive for long against superior land based air forces. Why do we expect the corvette, missile boat, or minesweeper to survive in the same environment without support?

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“Meanwhile, any combined arms approach in which some platforms rely on others for aspects of their defence gravitates a lot towards much smaller boats than anyone would call "corvette".”

The bigger problem for a blue water navy is that these missile boats lack the endurance and sea-keeping to cross the ocean. Thus blue water force is obliged to counter the small, cheap, and sexy fast attack craft with significantly larger warships, with less sexy and lower speed displacement hulls.

Another option is the mother ship concept where fast attack craft are carried to the area of operations by a much larger support vessel.

Smaller fast attack craft have the ability to carry heavy ASCM weapons, but have even less sensor capability than the corvette. *If* the fast attack craft can network with other sensor platforms and satellite then they can be effective. Otherwise fast attack craft are even less useful to a blue water navy than corvette, because they cannot get to the fight.

It is difficult to build a ship both small and capable of crossing an ocean safely, but there were many small ships used on routine oceanic escort duties; the Flower class repopularized the "corvette" category during WW2 as an Atlantic escort of less than 1,000 metric tons.-----You didn't get my motivation. I'm not concerned about how to hug China's coastline and survive. I'm interested in strategic defence, not strategic offence. And I'm interested in (a) deterring war and (b) turn the tide quickly and obviously so during an eventual war of necessity, in order to reach a quick peace. I'm not someone who's interested in preparations to go for the aggressor's government and root out the entire political party forever.The only phase of war that's worthy to be prepared for thoroughly is thus the phase up to the obvious turning point. This means I'm not interested in how to apply overwhelming power, for the ability to do so means you've already got the upper hand and should negotiate.

It may be that no fleet will close with a great power's shores unless it is already dominant, but the debate about corvettes is typically about how to achieve the strength required for such dominance, not about how to exploit said dominance. The exploitation is relatively easy (albeit not necessarily decisive enough if you have extremist demands).

Your initial comment was dismissing survivability concerns by claiming that the rest of the textbook would work out well. I consider that a very weak argument against the concerns brought forward in the blog text.

"Your initial comment was dismissing survivability concerns by claiming that the rest of the textbook would work out well. I consider that a very weak argument against the concerns brought forward in the blog text"

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You create a scenario that pits air power against corvettes, a ship class that will *never* have adequate air defenses due to the physical constraints of the hull, as well as the fiscal impracticality of trying to add the capability; and then discover that the corvette is going to come off badly.

There is nothing gained hereby your proclamation.

It is an obvious conclusion that was proven in the 1940s - surface ships are unable to withstand coordinated air attacks without support.

Text book or not, you either provided the support, accept that your force will be devastated, or you withdraw.